The invention relates to an optoelectronic module, an optoelectronic device, a method for manufacturing an optoelectronic module, as well as a use of an optoelectronic module. Such optoelectronic modules, optoelectronic devices, methods and uses can be employed in natural sciences, technology, medicine and daily life in various manners. An important field of application to which the invention, however, is not limited, is its use in the field of process technology, for example, for the purpose of drying and/or hardening materials and/or objects or for the purpose of a photochemical modification of workpieces. As an alternative or in addition, optoelectronic modules and optoelectronic devices of the type described below can, for example, also be used in the field of illumination, for example, in traffic engineering and/or in building services.
In particular, the invention relates to optoelectronic modules which are designed as what are called chip-on-board modules, either as a whole or in part. Such chip-on-board modules are modules which can be manufactured according to what is called chip-on-board technology (CoB), either as a whole or in part. According to chip-on-board technology, one or more unhoused semiconductor components (semiconductor chips) are directly mounted to a substrate, for example, a printed circuit board or another type of interconnect device. In general, the term of chip-on-board module therefore relates to an electronic assembly which includes at least one substrate as well as at least one unhoused (naked) semiconductor component mounted to a substrate. For example, such chip-on-board modules are used as luminous elements, as high-performance lamps (for example, as high-performance UV LED lamps), as photovoltaic modules, as sensors, or in any other manner. In particular, the optoelectronic modules suggested are optoelectronic chip-on-board modules having a plurality of optoelectronic components. Within the scope of the present invention, the optoelectronic components used therein may, for example, however not exclusively, be light-emitting diodes (LEDs) and/or photodiodes, particularly in the form of chips or other components, which are arranged in the chip-on-board module on a planar substrate, more particularly a substrate made of metal, ceramic or silicon, a metal-core or FR4 printed circuit board, a glass substrate, a plastic substrate, a metal matrix compound material, or similar substrates. These chip-on-board modules must be protected against mechanical damage and corrosion. To achieve this, it is tried to find solutions that are as compact and simple as possible.
Since, usually, protection in the form of housings on chip-on-board modules is complex in terms of costs and technology, planar potting of all or a plurality of components with a plastic-based potting material is known as practical prior-art alternative for protecting such chip-on-board modules. Along with other functional components, such as solder tracks and contacting elements, the optoelectronic components in chip-on-board modules, together with a planar substrate, can be protected against mechanical damage and corrosion by means of coatings.
Furthermore, a directivity of the optoelectronic modules plays an important role for many applications. For optoelectronic components, directivity generally describes an angular dependence of the strength of waves received or transmitted, which is usually related to a sensitivity and/or intensity in a main direction, i.e., along an optical axis of the optoelectronic components. In particular, a radiation intensity and/or a directional characteristic of the optoelectronic module usually plays an important role in optoelectronic modules which comprise one or more light-emitting diodes as optoelectronic components. This directional characteristic is a special from of the directivity and, in this case, describes the angular dependence of the electromagnetic field and/or the intensity of the electromagnetic waves emitted, in particular in the form of infrared, ultraviolet or visible light. Chip-on-board modules are to advantage in that light-emitting diodes can be applied onto the substrate with a high packaging density, this increasing the radiation intensity. In many cases, however, an additional optical system is used to influence the directional characteristic of the optoelectronic modules. For light-emitting optoelectronic modules as well as for photosensitive optoelectronic modules, this optical system can, for example, be one or more lens systems, for example what are called microlens systems. The lens systems can comprise one or more beam-forming elements the lateral extension of which can be in the sub-millimeter range to the decimeter range. In the optically active ranges of these microlens systems, there may, for example, be structures in the sub-millimeter range.
Due to the fact that the distances required between the optoelectronic components are short, more particularly due to the short pitch (centre-to-centre distance between neighboring optoelectronic components) typically used in chip-on-board modules, there are only a few known methods allowing the implementation of beam-forming microlenses above the individual optoelectronic components, for example, the individual light-emitting diodes of an array of light-emitting diodes, for example by means of an appropriate potting material.
For example, the post-published document, DE 10 2010 044 470, from the house of the Applicant of the present application describes a method for coating an optoelectronic chip-on-board module which comprises a planar substrate fitted with one or more optoelectronic components. Therein, use is made of a transparent UV- and temperature-resistant coating consisting of one or more silicones. According to the method, the substrate to be coated is pre-heated to a first temperature. Furthermore, a bank is applied which encloses an area or partial area to be coated of the substrate. This bank, as a whole or in part, is composed of a first thermally hardening, highly reactive silicone which hardens at a first temperature. This first silicone is applied to the pre-heated substrate. Furthermore, the area or partial area of the substrate that is enclosed by the bank is filled with a liquid second silicone, and the second silicone is hardened. Therein, it is also possible to apply quickly hardening lenses onto individual components of the substrate, particularly by means of the first silicone. In this manner, it is also possible to form microlens systems.
Furthermore, a method for coating an optoelectronic chip-on-board module is known from the likewise post-published document, DE 10 2010 044 471, that is also originating from the house of the Applicant of the present application. Again, the optoelectronic chip-on-board module comprises a planar substrate which is fitted with one or more optoelectronic components and includes a transparent UV- and temperature-resistant coating consisting of silicone. The method comprises a method step of potting a liquid silicone into a mould that is open at the top and comprises outside dimensions that correspond to the outside dimensions of the substrate or are in excess thereof. Furthermore, the substrate is introduced into the mould wherein the optoelectronic component or the optoelectronic components completely immerse(s) into the silicone. In a further method step, the silicone is hardened and cross-linked with the optoelectronic components and the substrate. Furthermore, the substrate provided with the coating consisting of the hardened silicone is removed from the mould.
Furthermore, an LED array which comprises a lens array for converging divergent light from each LED is known from U.S. Pat. No. 7,819,550 B2. The lenses each comprise a flat section and two curved sections. The lenses are not curved above the light-emitting diodes.
A method for manufacturing a white-light LED is known from US 2007/0045761 A1. Therein, use is made of an LED which emits blue light and use is made of phosphoruses which convert the light. Among other things, said document also describes the formation of optical systems above the light-emitting diodes, which are produced by means of a casting process that provides a seal against the atmosphere.
Furthermore, a method for encapsulating light-emitting diodes by means of a compression casting method is known from US 2010/0065983 A1. Therein, use is made of a tape for sealing during the casting process.
As a matter of principle, it is furthermore known to use reflectors as optical components. For example, U.S. Pat. No. 7,638,808 describes the use of microreflectors for LED arrays. Therein, use is made of a substrate which has cavities into which LEDs are inserted. Lateral walls of these individual cavities serve as reflector which can be adjusted in its design. The document also describes the use of an additional beam-forming potting process to close the cavities.
Despite the improvements described above and achieved for known optoelectronic modules, there is still a demand for optoelectronic modules with an improved directivity, more particularly a demand for optoelectronic modules with a high radiation intensity for specific applications. In particular, there is a demand for efficient light sources that can be mounted side by side and the lighting profile of which may have a high radiation intensity at an adjustable distance, wherein high homogeneity requirements are met at the same time and a sufficiently steep drop can be registered in the edge region. Such optoelectronic modules, more particularly modules of light-emitting diodes, are required for lithographic applications in the industrial production of the printing industry in order to reach a uniform and high-quality drying image of print colors and inks. High radiation intensities, for example, radiation intensities that are usually in excess of 100 mW/cm2, typically 1-20 W/cm2, up to 100 W/cm2, are usually required for reaching high process velocities with light sources that are as compact and energy-efficient as possible.